1. Field of the Invention
This invention relates to ophthalmic lens surfacing apparatus with particular reference to improvements in means for adapting lens surfacing tools to lens manufacturing machinery.
2. Description of the Prior Art
Ophthalmic lenses having semi-finished surfaces requiring final precision grinding and polishing are traditionally placed against preformed tools (laps) and oscillated thereover with a force applied to the lens-tool interface, i.e. by pressing the lens against the tool.
Since the operation requires a different tool (lap) for each different lens surface shape to be produced as well as periodic replacement of worn tools, it is customary to employ tool adaptors in lens surfacing machinery. These are fastened to tool spindles or other such tool supporting mechanisms of the machinery and afford means for readily manually replacing and/or changing tools. A typical prior art adaptor is illustrated in U.S. Pat. No. 3,916,574 wherein it can be seen that the customarily recessed rim of a tool is seated upon the marginal portion of the adaptor and keyed against rotational displacement to the extent that this is possible without sacrifice of a clearance between key and key slot which is sufficient to permit ready removal and replacement of tool.
It is the requirement for and provision of this clearance between key and key slot (one in the adaptor and the other in the tool) that has heretofore led to problems of back and forth rotational slippage of tools during side to side oscillation of lenses thereover in a surfacing operation. Wear upon the adaptor and/or tool caused by rotational slippage enlarges the key-key slot clearance and compounds the problem of slippage.
In surfacing operations employing relatively slow tool rotations, the prior art continuous back and forth rotational slippage induces adaptor and/or tool wear which is promoted by inclusions of lens abrading materials. This wear necessitates uneconomical replacement of parts and if allowed to reach extremes, it adversely affects the accuracy of curvature and finish of lens surfaces being worked. In high speed operations the aforesaid rotational slippage can develop into a chatter which accelerates tool or adaptor wear and similarly adversely affects workpiece finishes.
An object of the present invention is to prevent rotational slippage between tool and adaptor during lens surfacing operations but without sacrifice of the ease and convenience of tool removal and replacement afforded by traditional clearances between interfitting components of the tool and tool adaptor.
A more specific object is to retain in the construction of a lens surfacing tool and tool adaptor combination, the usual and optimum interfitting clearances while affording automatic clamping together of tool and adapter responsively to the application of lens surfacing pressure to the tool and wherein the clamping action is automatically released with relief of the lens surfacing pressure.
Other objects and advantages of the invention will become more readily apparent from the following description.